This invention relates to an antenna system and, more particularly, to an antenna system including a plurality of antennas which can be combined in various ways to provide a variety of directivities for the antenna system.
A prior antenna system of this type is disclosed in, for example, Japanese Patent Application Publication No. 2001-36327 A laid open for public inspection on Feb. 9, 2001, which corresponds to U.S. Pat. No. 6,498,589 which issued on Dec. 24, 2002 to S. Horii, one of the co-inventors of the present application, and assigned to the same assignee of the present application.
The antenna system disclosed in the above publication includes four unit antennas A, B, C and D which are oriented differently in such a manner that the directivity of each unit antenna is angularly spaced by 90xc2x0 from adjacent antennas. Selecting means is provided to select one of outputs of the individual unit antennas and adjacent pairs of the unit antennas. A directivity control pulse generator provides a four-bit selection control signal to the selecting means to achieve the selection. The directivity control pulse generator is provided with a directivity selecting switch, which changes the value of the selection control signal cyclically, from, for example, xe2x80x9c1000xe2x80x9d through xe2x80x9c1100xe2x80x9d, xe2x80x9c0100xe2x80x9d, xe2x80x9c0110xe2x80x9d, xe2x80x9c0010xe2x80x9d, xe2x80x9c0011xe2x80x9d, xe2x80x9c0001xe2x80x9d, and xe2x80x9c1001xe2x80x9d back to xe2x80x9c1000xe2x80x9d, each time it is operated. In response to such changes of the selection control signal, the output of the antenna system changes from, for example, the output of the unit antenna A, the combined outputs of the unit antennas A and B, the output of the unit antenna B, the combination of the outputs of the unit antennas B and C, the output of the unit antenna C, the combination of the outputs of the unit antennas C and D, the output of the antenna D, and the combination of the outputs of the unit antennas A and D, back to the output of the unit antenna A. In this way, the directivity of the antenna system is successively switched, for example, clockwise about the antenna system.
The directivity control pulse generator of the described antenna system can change the value of the four-bit control signal only in the above-described order. In other words, the switching of the directivity can be done only in one direction. Accordingly, when the directivity of the antenna system is being changed in the prescribed order to select the best directivity for receiving a desired radio wave, it is not possible to return back in the reverse order if the previous directivity is found to be better than the current one, but it is necessary for the four-bit control signal value to lap in the forward direction in the prescribed order to the previous value. Therefore, it has been required some time to attain the best directivity.
In the described antenna system, no correlation is established between the switching of directivity and the frequency of a desired radio wave. If the antenna directivity is different from one radio wave to another, the directivity selecting switch must be operated each time a different radio wave is to be received, in order to select a desired directivity for the antenna system. Therefore, it is troublesome to set the antenna system in the state to obtain the best directivity.
An object of the present invention is to provide an antenna system which can be rapidly set to have a desired directivity.
In an antenna system according to a first embodiment of the present invention, a plurality of directivities of an antenna system are successively scanned in a desired direction or order in order to find an optimum directivity to receive a desired radio wave. This scanning is done by operating first and second operating elements.
The antenna system according to the first embodiment has an antenna main body. A plurality of first angularly spaced antennas are disposed within the body in such a manner as to provide the antenna system with a plurality of directivities that enable the antenna system to receive radio waves in a first frequency-band coming toward the body from different first directions around the body. Radio waves in the first frequency band may be, for example, radio waves in the UHF band or the VHF band. The radio waves may be television broadcast radio waves in the UHF or VHF band.
By combining the directivities of the first angularly spaced antennas, it is possible to provide the antenna system with a plurality of directivities that enable the antenna system to receive radio waves in the first frequency band coming toward the body from second different directions which are between adjacent ones of the respective first directions.
First selecting means is disposed within the body. The first selecting means operates to select one output from the outputs of the individual ones and combinations of the first antennas.
Control means is provided separate from the main body. The control means provides a selection control signal to the first selecting means. The control means has first and second operating elements. Each time the first operating element is operated, the control means provides such a selection control signal as to successively scan, in the clockwise direction around the main body, the directivities. Each time the second operating element is operated, the control means provides such a selection signal as to successively scan the directivities of the antenna system in the counterclockwise direction around the main body.
Through the operation of the first operating element, the directivity of the antenna system can be successively switched or rotated clockwise, and, through the operation of the second operating element, the directivity can be successively switched counterclockwise. When an operator is switching the directivity successively clockwise, for example, he or she may find that a desired radio wave can be received most efficiently with the previously selected directivity, and, therefore, may try to reverse the directivity scanning direction to the counterclockwise direction. According to the present invention, such reversal is easy.
Level adjusting means may be disposed within the main body for enabling level adjustment of the output from an individual antenna or combination of individual antennas selected by the first selecting means. An amplifier or a variable attenuator, for example, may be used as the level adjusting means. The control means has a third operating element, in addition to the first and second operating elements, which, when operated, provides a signal commanding the level adjusting means to operate in an operating state represented thereby.
With this arrangement, when the radio wave receiving level is too high or too low, the third operating element may be operated to adjust the signal receiving level to an appropriate one.
The control means may include operating means for transmitting an optical signal in response to operation of the operating elements, and transmitting means provided separately from the operating means. The transmitting means receives the optical signal from the operating means and transmits the selection control signal to the main body. The operating means may include the third operating element in addition to the first and second operating elements.
With this arrangement, the operating means with the operating elements can be disposed at a location remote from the transmitting means, which makes it possible to provide remote controlling of the antenna system.
A plurality of second antennas may be disposed within the body, which are arranged to receive radio waves in a second frequency band coming from the first directions to the body. The second frequency band may be the UHF or VHF band, and the radio waves may be television broadcast signals. The second antennas also have respective directivities, which may be combined in various ways to provide the antenna system with directivities that enable the antenna system to receive radio waves coming to the body from the second directions between adjacent ones of the first directions.
Second selecting means is disposed in the body. The second selecting means selects one output from the outputs of individual ones and combinations of the second antennas. The control means provides such selection control signals to the first and second selection means that each time the first operating element is operated, the directivities of the antenna system for radio waves in the first and second frequency bands are successively scanned in the clockwise direction around the body. Each time the second operating element is operated, the directivities for the first and second frequency bands are successively scanned in the counterclockwise direction around the main body.
With this arrangement, radio waves in different frequency bands can be received in an optimum receiving condition.
A transmission path is provided between the body and the control means. Via the transmission path, the output of an individual one of the first unit antennas or an output of a combination of ones of the first unit antennas is transmitted to the control means, and power for operating the level adjusting means is transmitted from the control means to the body. The control means forms the selection control signal in the form of variations of the operating source voltage to be supplied to the transmission path.
Since the selection control signal is formed by changing the source voltage, the circuit can be simplified.
The control means may provide a tone signal as the signal for commanding the level adjusting means to operate.
It would be possible to change the operating source voltage to be transmitted via the transmission path to form a signal which commands the level adjusting means to operate in the manner represented by the signal. However, in such a case, the operating source voltage must be changed for all of the receiving directions, and in order to indicate how the level adjusting means should be operated also by means of changing the operating source voltage, the source voltage must be changed in a very complicated manner. In contrast, by the use of a tone signal in commanding the level adjusting means to operate, the change of the source voltage needs to represent the selection control signal only, which simplifies the circuit.
The control means may include pulse signal generating means which generates a pulse signal in response to operation of the first and second operating element, counting means which counts the number of pulses in the pulse signal, and selecting means operating means which generates the selection control signal determined in accordance with the count in the counting means. The counting means, after it counts a value corresponding to the sum of the number of the first and second directions from which radio waves come, i.e. the number of the UHF (VHF) directivities of the antenna system, desirably has its count returned to the initial value in response to the next pulse applied to it. The pulse signal generating means generates a pulse each time the first operating element is operated, and generates pulses equal in number to the number of the directivities provided by the first antennas (and, hence, second antennas), minus one (1) each time the second operating element is operated.
According to a second embodiment of the present invention, radio wave receiving channels are stored in memory means in association with the directivity of an antenna system, and the directivity of the antenna system is changed in response to a channel selected.
The antenna system according to the second embodiment, too, includes a main body, first antennas, and selecting means. The antenna system is provided with a tuner, which is a discrete unit. The tuner receives and demodulates an output from the selecting means. The tuner may be a television broadcast signal receiving tuner, for example, which may be for handling analog television broadcast and/or digital television broadcast signals. The tuner may be built in a television receiver, or a discrete unit.
The tuner includes a memory means, which stores therein selection control signals to be supplied to the selecting means for receiving a radio wave of a desired one of a plurality of broadcast channels in response to selection of that channel. When a desired channel is selected in the tuner, a selection control signal for the selected channel is read out from the memory means and supplied to the selecting means.
When the tuner is operated to designate a desired channel, an antenna or antennas by which the radio wave of the designated channel can be received in an optimum condition is selected. Accordingly, there is no need to separately switch or select the antennas and the channels, which increases workability of the antenna system.
Level adjusting means is disposed in the main body for adjusting the level of the output from an individual unit antenna or a combination of the unit antennas as selected through the selecting means. The level adjusting means may be an amplifier or an adjustable attenuator. In addition to the selection control signals, level control signals indicating the states to which the level adjusting means is to be adjusted are stored in the memory means being correlated with the respective broadcast channels to be received. When the tuner is operated to select a desired channel, the level control signal for the selected channel is read out of the memory means and supplied to the level adjusting means.
With this arrangement, the level adjusting means adjusts the level of the antenna output so as to provide optimum reception of the desired channel.
If the broadcast channels to be received are digital television broadcast channels, the respective selection control signals are determined based on a bit error rate generated by the tuner, and if the broadcast channels to be received are analog television broadcast channels, the selection control signals are determined based on a signal reception level at the tuner.
Whether digital television broadcast waves can be received well or not depends on a bit error rate realizable in a tuner. Whether analog television broadcast waves can be received well or not depends on a received signal level at the tuner. The selection control signals are so determined as to provide an optimum bit error rate and an optimum received signal level.
A transmission path is provided between the main body and the tuner for transmitting an output of an individual unit antenna or a combination of outputs of unit antennas to the tuner. The tuner sends the selection control signals via the transmission path. For sending the selection control signal to the transmission path, modulating means may be provided which outputs a modulation signal formed of a carrier modulated with the selection control signal, and demodulating means may be provided in the body for demodulating the modulation signal back to the selection control signal.
With this arrangement, the selection control signals can be transmitted through the transmission path, no extra transmission paths for the selection control signals are required.